Users can execute applications on their mobile client devices to receive posts and collections of content published by other users. For example, a user may browse content within an application and select a content item (e.g., slideshow, article) for viewing. When the content is requested, the server handling the request must assemble the content, some of which may be provided by third parties, on-the-fly and send the assembled content to the user before the user notices a delay. The limited amount of time and limited network bandwidth constrain how content is selected for display.